Cutting bit



Sept. 29, 1942.

H. M. MORROW' CUTTING BI T Filed Oct. 3, 1940 fia. 4

fia 5 INVENTOR. Maw A4. Mo/mow Patented Sept. 29, 1942 CUTTING BIVTHarry M. Morrow, Canton, Ohio, assignor to The Bowdil CompanyApplication October 3, 1940, Serial No. 359,508 A 6 Claims. (01. 262-33)My invention relates in general to cutting bits and more particularly tobits for cutting coal or other substances.

In the mining of coal or other substances, a cleft is cut in the lowerlevel of the vein by means of a cutter bar around which revolves a powerdriven endless chain carrying a plurality of staggeredly arrangedcutting bits constituting the subject matter of this invention. Theshelf formed by the cleft is subsequently broken off by means ofexplosives or other suitable methods. When cutting the cleft, in theinterest of economy and the saving of power, it is highly desirable thatthe cutting bits be not only strong and durable but also eificient inoperation andv free from drag.

An object of my invention is the provision of a cutting bit whichrequires a minimum amount of power tooperate.

Another object of my invention is the provision of a cutting bit whichproduces very little drag.

Another object of my invention is the provision of a cutting bit whichhas a greater cutting clearance as the bit wears away.

Another object of my invention is to make the cutting clearance of thebit increase in substantial proportion to the amount that the cuttingpoints of the bit wear away.

Another object ofmy invention is to make my bit have relatively narrowcutting faces for a substantial. distance to give longer wear.

Another object of my invention is the provision of a cutting bit whichis durable and adapted to cut through hard substances.

Another object of my invention is the provision of a longitudinaldouble-ended bit having the shape of a minor segment of a double-concavedisc.

Other objects andv a fuller understanding of my invention may be had byreferring to the following description and claims, taken in conjunctionwith the accompanying drawing, in which:

Figure 1 shows a front elevational View of my new and improved cuttingbit;

Figure 2 shows a side elevational View of my new and improved cuttingbit as shown in Figure 1;

Figure 3 shows a cross-sectional View of my bit, taken along the line3-3 of Figure 2;

Figure 4 shows a cross-sectional view of my bit, taken along the line4-4 of Figure 2;

Figure 5 shows a cross-sectional view of my bit, taken along the line 55of Figure 2;

Figure 6 shows a front elevational view of a modified form of my cuttingbit;

Figure 7 shows a side elevational view of the bit in Figure 6;

Figure 8 shows a front elevational view of a further modified form of mybit; and

Figure 9 shows a side elevational view of the bit shown in Figure 8.

With reference to Figures 1 to 5, inclusive, my improved cutting bit issolid and may be made of steel, shaped by forging or in any othersuitable fashion. In front elevation, the cutting face .ll] of my bit issubstantially diamond-shaped and has a relatively wide central portion,II and two relatively narrow opposite edge portions l2 and I3. Thecontour of the side edges l4, l5, l6 and ll of the front cutting faceI!) between the relatively wide central portion l0 and the relativelynarrow opposite edge portions l2 and I3 are depressed, arcuate, orconcaved, and form cutting points l8 and I9 at opposite ends of the bit.

The side clearance faces 20 and 2| of my bit are substantially identicaland are shaped like the segment of a circle. The side clearance faces 20and 2| converge toward the rear edges thereof and meet in a relativelysharp juncture 22 which curves in a general longitudinal directionbetween the opposite cutting points I8 and I9, see Figures 2, 3, 4 and5. The side clearance faces between the relatively wide central portionand the relatively narrow opposite edge portions [2 and I3 aredepressed, arcuate, or concaved to produce a greater cutting clearanceas the cutting points wear away. The shape of my bit constitutes a.minor segment of a double-concave disc. That is to say, the shape of mybit in Figures 1 to 5, inclusive, is substantially the same as thatwhich would be produced if a disc having double-concave marginal edgesurfaces were cut upon acord of the circumference, the

arcuate juncture 22 being equivalent to the arc of t'he circumference ofthe disc and the front face l0' being equivalent to the plane producedby the cutting action.

Thebits are removably mounted in the lugs of the endless power drivenchain which revolves around the cutter bar. When one of the cuttingpoints of the bits wears away the bits are reversed, giving a doublecutting life to the bits. The cutting points may be treated or hardenedby any suitable means such as, for example, by depositing a hardenedmetal thereon. The bits areheld in the chain lugs at a slight forwardangle as shown in Figure 2.

, The provision of the varying cutting clearance is progressively shownin Figures 3, 4 and 5. In

the region near the cutting points shown by Figure 3, the clearance israther small. At the cutting points of the bit, the drag does not havean opportunity to manifest itself since the horizontal distance of theside walls across the bit in the rear of the cutting faces is small, andfor this reason the cutting clearance in the region of the cuttingpoints may be rather small without producing any substantial increase inthe drag of the bits in the cutting operation. By making only a verysmall clearance in the region of the cutting points, the cross-sectionalarea of the cutting points may be kept at a maximum, thereby givingadditional strength to the cutting points which are subjected to a greatdeal. of strain during the cutting operation. As the cutting points wearaway, the horizontal distance of the side clearance faces 20 and 2| ofthe bit in rear of the cutting face increases, and for this reason anadditional side clearance face drag would tend to be produced. In orderto reduce this drag of the side clearance faces because of theadditional cutting side wall depth of the bit, I provide for making theside clearance faces 20 and 2| of the bit depressed, arcuate orconcaved, so that a greater clearance is produced as the cutting pointsof the bits wear away. The cutting clearance is indicated by thereference character 23 and the increase in cutting clearance isillustrated by the increased lateral space upon opposite sides of thecross-sectional views of Figures 4 and 5 over Figure 3, taken atdifferent horizontal cutting sections through the bits. Therefore, withmy improved cutting bit the drag is kept at a low minimum, regardless ofthe amount of wear that might occur upon the bits. Another resultgrowing out of the depressed, arcuate, or concaved side clearance faces20 and 2! of my cutting bit is the fact that the cutting faces remainrelatively narrow for a considerable distance and do not begin tobroaden until the side clearance faces 20 and 2| approach the centralbody portion ll of the bit. Moreover, the clearance is proportionatelydistributed throughout the entire life of the bit, so that the drag isalways maintained at a low minimum value.

In Figures 6 and '7, I show a modified arrangement of my improved bit,in that the portion 24 of the side clearance faces in the region of therelatively wide central portion is substantially flat to give lateralsupport to the bits in the chain lugs. The shape of my modified bit inFigures 6 and '7 is substantially the same as that which would beproduced if a disc having double-concave marginal edge surfaces and acentral fiat portion were out upon a cord of the circumference of thedisc intersecting a small part of the fiat portion to make the fiat area24.

In Figures 8 and 9, I show a further modified arrangement of my improvedbit in that the portion 25 of the side clearance faces in the region ofthe relatively wide central portion is substantially convex in both ageneral longitudinal direction and a transverse direction to givelateral support to the bits in the chain lugs. The shape of my modifiedbit in Figures 8 and 9 is substantially the same as that which would beproduced if a disc having double-concave marginal edge surfaces and acentral convex portion were out upon a cord of the circumference-of thedisc intersecting a small part of the convex portion to make the convexarea 25.

Although I have described my invention with a certain degree ofparticularity, it is understood that the present disclosure has beenmade only by way of example and that numerous changes in the details ofconstruction and the combination and arrangement of parts may beresorted to without departing from the spirit and the scope of theinvention as hereinafter claimed.

I claim as my invention:

1. A longitudinal double-ended bit comprising a solid piece of metalhaving a longitudinal front cutting face and side clearance faces, saidfront cutting face having a relatively wide central portion andrelatively narrow opposite edge cutting portions, the contour of theside edges of the front cutting face between the said relatively widecentral portion and the said relatively narrow opposite edge cuttingportions being concaved and forming cutting points at opposite endsthereof, the contour of the front edges of the side clearance facesmeeting with the side edges of the front cutting face and beingsubstantially straight in side elevation and the contour of the rearedges of the side clearance faces meeting in a relatively narrowjuncture, said juncture in side elevation being curved in a generallongitudinal direction between the opposite cutting points, each of saidside clearance faces beginning at a central place near the front edgethereof and substantially mid-way of the cutting points convergingtoward the narrow juncture in a radial direction, each of said sideclearance faces being also concaved in said radial direction andproducing a greater cutting clearance as the cutting points wear away.

2. A longitudinal double-ended bit comprising a solid piece of metalhaving a longitudinal front cutting face and side clearance faces, saidfront cutting face having a relatively wide central portion andrelatively narrow opposite edge cutting portions, the contour of theside edges of the front cutting face between the said relatively widecentral portion and the said relatively narrow opposite edge cuttingportions being concaved and forming cutting points at opposite endsthereof, the contour of the front edges of the side clearance facesmeeting with the side edges of the front cutting face and beingsubstantially straight in side elevation and the contour of the rearedges of the side clearance faces meeting in a relatively narrowjuncture, said juncture in side elevation being curved in a generallongitudinal direction between the opposite cutting points, each of saidside clearance faces beginning at a central place near the front edgethereof and substantially mid-way of the cutting points convergingtoward the narrow juncture in a radial direction, each of said sideclearance faces being also concaved in said radial direction andproducing a greater cutting clearance as the cutting points wear away,the curvature of the said juncture in a general longitudinal directionbeing substantially an arc of a circle.

3. A longitudinal double-ended bit comprising a solid piece of metalhaving a longitudinal front cutting face and side clearance faces, saidfront cutting face being substantially diamond-shaped and having arelatively wide central portion and relatively narrow opposite edgecutting portions, the contour of the side edges of the front cuttingface between the said relatively wide central portion and the saidrelatively narrow opposite edge cutting portions being concaved andforming cutting points at opposite ends thereof, the contour of thefront edges of the side clearance faces meeting with the side edges ofthe front cutting face and being substantially straight in sideelevation and the contour of the rear edges of the side clearance facesmeeting in a relatively narrow juncture, said juncture in side elevationbeing curved in a general longitudinal direction between the oppositecutting points, each of said side clearance faces beginning at a centralplace near the front edge thereof and substantially mid-way of thecutting points converging toward the narrow juncture in a radialdirection, each of said side clearance faces being also concaved in saidradial direction and producing a greater cutting clearance as thecutting points wear away.

4. A longitudinal double-ended bit comprising a solid piece of metalhaving a longitudinal front cutting face and side clearance faces, saidfront cutting face having a relatively wide central portion andrelatively narrow opposite edge cutting portions. the contour of theside edges of the front cutting face between the said relatively Widecentral portion and the said relatively narrow opposite edge cuttingportions being concaved and forming cutting points at opposite endsthereof, the contour of the front edges of the side clearance facesmeeting with the side edges of the front cutting face and beingsubstantially straight in side elevation and the com tour of the rearedges of the side clearance faces meeting in a relatively narrowjuncture, said juncture in side elevation being curved in a generallongitudinal direction between the opposite cutting points, each of saidside clearance faces beginning at a central place near the front edgethereof and substantially mid-way of the cutting points convergingtoward the narrow juncture in a radial direction, each of said sideclearance faces being also concaved in said radial direction andproducing a greater cutting clearance as the cutting points wear away,the curvature of the said juncture in a general longitudinal directionbeing substantially an arc of a' circle, said relatively wide centralportion being substantially flat.

5. A longitudinal double-ended bit comprising a solid piece of metalhaving a longitudinal front cutting face and side clearance faces, saidfront cutting face having a relatively wide central portion andrelatively narrow opposite edge cutting portions, the contour of theside edges of the front cutting face between the said relatively widecentral portion and the said relatively narrow opposite edge cuttingportions being concaved and forming cutting points at opposite endsthereof, the contour of the front edges of the side clearance facesmeeting with the side edges of the front cutting fa'ce and beingsubstantially straight in side elevation and the contour of the rearedges of the side clearance faces meeting in a relatively narrowjuncture, said juncture in side elevation being curved in a generallongitudinal direction between the opposite cutting points, each of saidside clearance faces beginning at a central place near the front edgethereof and substantially mid-way of the cutting points convergingtoward the narrow juncture in a radial direction, each of said sideclearance faces being also concaved in said radial direction andproducing a greater cutting clearance as the cutting points wear away,the curvature of the said juncture in a general longi-- tudinaldirection being substantially an arc of a circle, the portion of each ofsaid side clearance faces in the region at the said central place beingconvex in said radial direction and gradually meeting in a compoundcurve with the concaved surface of each of said side clearance faces.

6. A longitudinal double-ended bit comprising a solid piece of metalhaving a. longitudinal front cutting face and concave side clearancefaces, the shape of said bit being a minor segment of a disc havingconcave opposite walls intermediate its center and longitudinal edge.

HARRY M. MORROW.

